Court? You have seconds to react. You're too far away from both girls to interveine. Even if you ran up to tackle the knife weilder, the other girl would've been stabbed by then. We're not talking about a future punishment, were talking about a dangerous act and how you can stop it instantly before one person looses a life. Would you rather shoot the attacker, or do nothing and watch a girl die? Then the other girl goes to jail and has no life, thus meaning both girls lives are ruined. Instead, one girl was saved. Seriously what would you do? I would like to know